Field of the Invention
The present invention relates generally to a bush assembly used for securing an elongated member to a stationary base. More specifically, the invention relates to a bush assembly or a slipping bush which can be used for fixing the upper arm of a double wishbone type suspension to a vehicle body.
According to our previous unpublished invention, the upper arm of a double wishbone type suspension is fixed to a vehicle body by means of a bush assembly and a supporting pin inserted into the inner space of the bush assembly. As shown in FIG. 1, such a bush assembly generally comprises an inner cylindrical member 1, an outer cylindrical member 2 arranged so that the axis thereof coincides with that of the inner cylindrical member 1, and a rigid sleeve 3 provided therebetween. The rigid sleeve 3 is fixed to the inner surface of the outer cylindrical member 2 by means of an elastic member 4, and slidably engages the outer surface of the inner cylindrical member 1 via a slipping member 5.
In such a bush assembly, since the slipping member 5 is slidably in contact with the inner cylindrical member 1 and the rigid sleeve 3, if muddy water or the like gets into the interface between the slipping member 5 and the inner cylindrical member 1 or the rigid sleeve 3 from the outside, the bush assembly tends to corrode and wear, so that the duration of life of the bush assembly is decreased.
In order to prevent muddy water or the like from getting into the interface, in a the bush assembly shown in FIG. 1, a sealing member 6 is provided in an annular space defined by an end portion 1a of the inner cylindrical member 1 and the greater diameter portion 3a of the rigid sleeve 3. A related construction is illustrated in the Japanese Patent First (unexamined) Publication Showa 62-127934.
In our bush assembly of FIG. 1, the outer portion 6a of the sealing member 6, in which a ring member 7 is embedded for reinforcement, is fixed to the rigid sleeve 3. On the other hand, and the inner portion 6b thereof is brought into contact with the end portion 1a of the inner cylindrical member 1. With such a construction, there are the following disadvantages. Since the inner portion 6b of the sealing member 6 must be compressed in a radial direction to engage the end portion 1a of the inner cylindrical member 1 in order to achieve a desired seal, pressure must be applied to the bearing surface of the inner portion 6b of the sealing member 6, and the inner portion 6b tends to wear. In addition, when the inner cylindrical member 1 rotates in relation to the rigid sleeve 3, the inner portion 6b of the sealing member 6 can not easily slide around the inner cylindrical member 1, so that a bad seal tends to occur.